There is known a solar collector with a vacuum tube comprising an outer tube and an inner tube, the tubes being concentric and substantially cylindrical. Each tube is closed at one of its ends, and the tubes are sealed one to the other at the other of their ends. The solar collector comprises a solar radiation absorption layer arranged on an outer surface of the inner tube and oriented towards the outer tube. The solar collector includes a heat pipe having a hot part (evaporator) laid out inside the inner tube, a cold part (condenser) arranged outside the tubes, and a reservoir containing a heat pipe fluid, and extending over the hot part and the cold part. The hot part of the heat pipe comprises the reservoir in the shape of a cylinder substantially centered on the axis of the inner tube, and two fins fixed to the cylindrical reservoir, in a diametrically opposite manner, and mechanically and thermally linking the reservoir to the inner surface of the inner tube. The reservoir has a diameter that is much smaller than that of the inner tube.
Thermal conduction up to the absorption layer is not optimal, bringing about significant heat losses.